Q: Mini dv to HDMI adapter

Over the last several months I have enjoyed showing my computers screen up on my nice HD television via a minidv to hdmi adapter I got off amazon.  The last few weeks, sometimes when I'd plug it in it would only show the default lion destop image (which is not my current wallpaper).  Anything I would open on the computer would not show on the TV, just the picture of a galaxy.  In the begining I would just restart my computer and it would work again. Now it's not going away. I have restarted my computer several times and reset the pram because I dont know any other troubleshooting steps other than that. Is there like a hotkey to show whats actually on my computer and thats just like a standby mode or something? Any help would be much appreciatted, Todd

p.s. also the time when it stopped working completly is after I got my display and battery replace from the applestore because they were having issues, not sure if that would really have anything to do with it though.